AKTIFIT Q is an activated SILFIT Z 91, produced by modifying the surface with a methacrylic silane. The by-products split off during the treatment reaction are largely removed during the production process which firmly attaches the silane to the filler surface. This helps minimize undesirable side effects, as they are potentially encountered with in-situ mixing (direct addition of silane to the compound). A special process technology during production of AKTIFIT Q provides high hydrophobicity as well as outstanding low moisture absorption even under very humid conditions. During compounding, the hydrophobic methacrylic groups groups of AKTIFIT Q ensure good wetting and excellent dispersion in the matrix polymer. In addition, in polymers with suitable functional groups and presence of free radicals, i. e. peroxides, AKTIFIT Q can be covalently bonded into the polymeric matrix. In polar polymers the use of this grade leads to high composite strength via strong interaction.